This invention pertains to the art of pressure sensing devices and, more particularly, to a device for identifying pressure differentials.
The invention is particularly applicable to a draft gauge for identifying the draft pressure of a stove or furnace flue pipe. However, it will be appreciated to those skilled in the art that the invention could be readily adapted for use in other environments as, for example, where similar pressure sensing devices are employed for sensing pressure differential.
As energy costs have risen, an increased need has arisen for instruments indicating the operational characteristics of stoves and furnaces. It is particularly important in solid fuel stoves or furnaces that the burning wood or coal be exposed to a proper draft for maximizing burning efficiency. Draft is caused by a pressure differential between the pressure in the flue pipe and the pressure outside of the flue pipe in the room of the burning stove.
It is well known that liquid manometers may be employed for gauging small pressure differentials. Conventional manometers typically comprise a U-shaped tube, one end of which is open to the atmosphere, and the other to the region where the pressure is to be measured. If the pressure is different from atmospheric, the liquid with which the manometer is partially filled with stand higher in one leg of the tube than the other. It is also conventionally known that to make the instrument more sensitive, both legs may be inclined so that a given vertical displacement of the meniscus in one leg relative to the other will travel a considerably larger distance along the scale.
Prior differential manometers have suffered from a number of inherent problems, foremost of which is that most differential manometers have not been designed for use in the home and, specifically, the living area and therefore typically comprise excessively large, unwieldy, aesthetically unattractive and expensively produced devices. In particular, most prior differential manometers which could be employed on a flue pipe would be so large as to be impractical for home use. Those differential manometers which would be sufficiently compact to be practically employed in a home have suffered from high price and the problem of having a tube bore so small that flammable gauge oil with low surface tension had to be employed or else the meniscus would lack sufficient sensitivity to the relevant changes in pressure of a flue pipe.
Another particular problem with prior art differential manometers has been the use of a manometer fluid which could be exposed to the high temperatures of a stove flue pipe and, yet, resist evaporation while maintaining thermal stability so as to be practically useful for an advantageous period of time.
A further problem with prior art differential manometers has been lack of an economical leveling mechanism to be used for maximizing draft gauging efficiency in a compact manometer tube. In differential manometers that have not been open ended, it has not been particularly critical to maintain leveling for efficient operation.
The present invention contemplates a new and improved device which overcomes all of the above-referred to problems. The new differential manometer is reliable, simple in design, economical to manufacture, readily adaptable for use with a stove or furnace in a home living area or basement, easy to install, easy to adjust and employ, and provides improved draft gauging and ease of reading.